1. Field of the Invention
The present invention relates to a polypropylene resin composition and a molded article made of the polypropylene resin composition. More particularly, the present invention relates to a polypropylene resin composition having excellent coating property, peeling strength and elasticity and a protective strip for automobiles made of the polypropylene resin composition.
2. Description of the Related Arts
For automobile bumpers, compositions of polypropylene (PP) and ethylene-propylene rubber (EPR) have heretofore been used as materials. Polypropylene has extremely inferior coating property because it has no polar group in the molecule and chemically inert. For coating of a bumper made of such a composition, etching treatment with trichloroethane or the like is indispensable. This situation is not limited to coating of automobile bumpers. For coating of an article made of a polypropylenic composite material, it is the general practice that the article is processed with pretreatment of etching with trichloroethane to obtain practical coating strength (refer to Shosaku Yamamoto and Mikio Uchida, Jitsumu Hyomen Gijutsu, Vol. 31, Number 10, Page 440 (1984)).
However, trichloroethane causes environmental destruction, such as ozonosphere destruction, and thus a method using trichloroethane in coating must be avoided.
As materials to replace trichloroethane, surface active agents in the form of alkaline aqueous solutions can be mentioned. However, these surface active agents show low washing and dissolving ability when they are applied to PP and cannot be used for coating of an article made of a polypropylenic composite material, such as a bumper made of the composition described above.
On the other hand, methods of improving the property for coating by blending a polar substance with PP have been reported. As examples of such methods, a composition prepared by adding polyvinylphenol to a PP resin (Japanese Patent Application Laid-Open No. Heisei 3(1991)-9941), and a composition prepared by adding a copolymer of ethylene and carboxylic acid compound to a PP resin (Japanese Patent Application Laid-Open No. Heisei 3(1991)-278862) can be mentioned. However, these compositions do not always have sufficient adhesion of the coated layer when bumpers prepared by using these materials are coated after pretreatment of washing with a watery system.
Furthermore, polyvinyl chloride (PVC) has been frequently used as a material of molded parts of automobiles, such as protective strips, when a pretreatment with trichloroethane or the like is not applied. PVC occasionally generates toxic gas when it is burned. Therefore, application of PP particularly to protective strips for automobiles has been urgently desired.